[1] Univ Bristol, Sch Social & Community, MRC Integrat Epidemiol Unit, Bristol, Avon, England
[2] Natl Univ Ireland Univ Coll Cork, Dept Epidemiol & Publ Hlth, Cork, Ireland
[3] Mercy Univ Hosp, HRB Clin Res Facil Cork, Cork, Ireland
[4] Natl Univ Ireland Univ Coll Cork, Sch Med, Cork, Ireland
[5] Cork Univ Matern Hosp, Natl Perinatal Epidemiol Ctr, Cork, Ireland